Boev, V. I.; Kushnir, V. N.; Shevchuk, M. I.; Dombrovskii, A. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1980 , vol. 16, # 5 p. 550 - 552 Khimiya Geterotsiklicheskikh Soedinenii, 1980 , # 5 p. 701 - 704